LPG misfire after EGR valve replacement

[Jiranimothe1]

Hello, in dire need of help. I run a Subaru Legacy LPG converted 2004, EZ30. Not sure what LPG system I have.
The long story short is that I had a lean bank code with misfires and been battling a vacuum leak for awhile. Although the code the car could still run on both petrol and LPG with additional misfires, but it ran relatively ok. I’ve fixed most of the leaks and for the ones I could I had a Subaru specialist find them, which ended up being the last one on the EGR valve which they then replaced. Since taking the car, it still runs with very low RPM as the misfire still continues and no engine codes at all on petrol. but now as soon as I switch to LPG it’s just stutters and engine light comes on and flashes like mad. As soon as I switch back to petrol all good.
Any advice as to what could cause it as I know that to change the EGR the manifold had to be taken off and the LPG system caused the garage difficulties to access it. Could my nee problem under LPG be cause by the Garages poor work? Or after fixing the leak my LPG now need configuration under new airflow?

[jonathan_d]

Have you done a compression test? Probably best to start by checking if it has any valves left.

[Brian_H]

If its running well on petrol and awful on gas, a simple thing that might explain it is if the injector wiring has got mixed up (so the petrol and gas injectors don't match up to the correct cylinders). It could also be that the lpg side is some way out of adjustment as well, but that shouldn't suddenly happen by itself. Any ideas what codes are being generated when the engine light comes on? Those might give a point towards specific cylinders.

Its also possible that rather than mixing them up, they have either not got one of the hoses back in place properly allowing air to enter, or kinked it causing little to no lpg to get to one cylinder. Or could just be a failure thats coincided with trying to fix the other faults.

Photos of the install may help to identify what you have got?

[Pinger]

and engine light comes on and flashes like mad.

That might be more of a clue than it is being credited with.
I'm pretty sure I read on a GMT400 forum that the EML flashing is a sign on its own and in the case of GMT400s it means 'weak mixture' IIRC. Might be worth checking if Subaru have configured it to a single/dedicated meaning and/or it is a universal sign of weak mixture.

[LPGC]

The engine warning light usually flashes when the petrol ECU knows the engine is misfiring.

I would echo the advice of BrianH above.

[Jiranimothe1]

Oh wow those are quick reply’s thank you.

As for compression I’ve not done it, however in the past I had a code for lean bank 2 (P0174) and in addition now and again would show cylinders 1,3,5 misfiring. Which side are they on, as I understand it’s the drivers side and bank 2 is passenger side, is that correct?

However, the above used to be a problem under both petrol and LPG, but it would still run well enough without immediate worry. Now that all air leaks have been fixed there is no CEL light under petrol, but as soon as switching to LPG the CEL starts flashing (not steady at all) for a fairly long while like a full minute. So I got worried so switched it back to petrol, and the CEL immediately disappeared and engine was running well again (relatively speaking, with low RPM).

Brian H, thank you I will be taking it back to the garage to see if so they can double check their work, unfortunately they are not LPG specialists as I wanted to first fix any petrol problems I had with a Subaru specialist. So they might not know what they are doing with the LPG reconnection if anything had to be taken apart for the EGR valve replacement. I will try to take a photo of it later today.

[Pinger]

The engine warning light usually flashes when the petrol ECU knows the engine is misfiring.

You've jogged the bit of my memory I needed yesterday.
Flashing EML is to highlight misfiring and does so to prevent raw fuel burning up the cats - if I've remembered that bit correctly...